Field of the Invention
The present invention relates to an electro-optical module with a housing in which a carrier plate or circuit board is accommodated. The plate carries at least one optical element, electrical circuit elements, and electrical terminal elements.
An electro-optical module of the generic type is described in U.S. Pat. No. 5,475,783 and published European patent application EP 0 646 816 A2. In the prior art module, a circuit board with an optical element is so disposed in a housing transverse to the optical axis of the module, that the optical element lies on the optical axis. The carrier plate of the prior art module is fashioned in accordance with the type of printed circuit board and comprises electronic components which are connected to one another by printed interconnects. In addition, the front side of the carrier plate of the prior art module is provided with electrical terminal elements. With the aid of these electrical terminal elements, the known electro-optical module can be electrically connected to interconnects on a printed circuit board, for instance, by placing the module onto the printed circuit board in customary fashion. The number of electrical circuit elements that can be accommodated on the carrier plate is limited given a prescribed structural shape of the housing of the known electro-optical module.
If additional electrical circuit elements are to be allocated to the known electro-optical module, the obvious solution is to accommodate these additional electrical circuit elements on an additional board, and to install this additional printed board behind the electro-optical module (with reference to the optical axis) on a printed circuit board; the electrical connection to the electro-optical module is produced via the latter printed circuit board. Not only does this require additional expense, but it also demands additional space on the board; moreover, the routing from the additional printed board to the electro-optical module and vice versa by way of the printed circuit board can adversely affect the transferred signalsxe2x80x94that is to say, the circuit with the circuit elements. U.S. Pat. No. 4,926,433 describes a laser unit for a laser printer wherein additional electrical circuit elements besides a laser diode are arranged on a carrier plate. The circuit elements are disposed on the side of the carrier plate which is averted from the laser unit. However, the carrier plate is not situated in a housing.
It is accordingly an object of the invention to provide an electro-optical module with a housing, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which allows equipping the electro-optical module with additional electrical circuit elements at relatively small expense while a compact design is maintained.
With the foregoing and other objects in view there is provided, in accordance with the invention, an electro-optical module, comprising:
a housing having a wall;
a carrier plate with at least one optical element, electrical circuit elements, and electrical terminal elements accommodated in the housing;
a circuit board fastened externally on the wall of the housing and directly electrically connected to the carrier plate; and
additional electrical circuit elements disposed on the circuit board outside the housing.
In accordance with an added feature of the invention:
the carrier plate and the circuit board are disposed parallel to one another and oriented transverse to an optical axis of the electro-optical module; and
the circuit board is formed with external electrical terminal portions of the electro-optical module on one front side thereof.
In accordance with a concomitant feature of the invention, the carrier plate has electrical terminal elements, and the circuit board is electrically connected to the electrical terminal elements at a region of a front side opposite the front side having the external electrical terminal portions.
With the above and other objects in view there is also provided, in accordance with the invention, an electro-optical module with a housing, comprising:
a carrier plate with at least one optical element, electrical circuit elements, and electrical terminal elements accommodated in the housing;
a circuit board at least partly forming a wall of the housing and additional electrical circuit elements disposed on the circuit board, wherein:
the additional electrical circuit elements are arranged on the circuit board outside the housing; and
the circuit board is directly electrically connected to the carrier plate.
In other words, the objects are achieved by disposing additional electrical circuit elements in an electro-optical module on a circuit board which either is fastened externally on the wall of the housing of the electro-optical module or is part of the wall of the housing of the electro-optical module. The additional electrical circuit elements are arranged outside the housing on the circuit board, and the circuit board is directly electrically connected to the carrier plate.
A substantial advantage of the inventive solution is that the additional electrical circuit elements are situated at the smallest imaginable remove from the housing of the electro-optical module, being arranged outside the housing on a circuit board which is fastened on the wall of the housing or which forms part of the wall; therefore, the routing between the carrier plate and the circuit board is quite short, and disturbances by the electrical connections are substantially prevented. Another advantage is that the space requirement for the circuit board and the additional circuit elements is small owing to the direct connection of the circuit board to the carrier plate.
In the inventive variant wherein the circuit board is fastened outside on the wall of the housing, the circuit board can be equipped with the additional electrical circuit elements in customary fashion and then fastened to the wall of the housing.
The inventive variant in which the circuit board is part of the wall of the housing of the electro-optical module is particularly advantageous in view of the space requirement. In this variant of the invention, a separate circuit board for accepting the additional electrical circuit elements is completely forgone in that a part of the wall of the housing is used as a circuit board.
In the inventive electro-optical module, the carrier plate and circuit board can be configured in or at the electro-optical module various ways and in various spatial configurations.
But it is considered particularly advantageous when the carrier plate and circuit board are oriented transverse to the optical axis of the electro-optical module in parallel planes, and when the circuit board comprises external electrical terminal portions of the electro-optical modules on one front side. This embodiment is characterized by a particularly compact design. The front side is the bottom edge of the module at which the fastening on the printed circuit board is carried out.
This compact design is furthered by the electrical connecting of the circuit board to the electrical terminal elements of the carrier plate in the region of the front side opposite the front side with the outer electrical terminal portions.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an electro-optical module with a housing, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.